(I) Green patches like woods on the outskirts of a large metropolitan city, also parks in the city keep the air of the city clean. (II) It is very expensive to keep such parks in a city. (III) However, they have to be maintained since they contribute so much to the health of the people. (IV) Birds chirp and twitter on the trees in the parks. (V) Both the government and the municipal authorities should make every effort to maintain and even add to the green patches in the city as they serve like the lungs of a city.